Patent document 1: U.S. Pat. No. 2,689,380
Patent document 2: JP-B-31-2452
Patent document 3: JP-B-41-1868
Patent document 4: JP-B-61-28846
Patent document 5: JP-B-62-33275
Polytetrafluoroethylene resins (hereafter abbreviated as PTFE) are widely used in sliding members such as bearings since they excel in self-lubricating properties and have low coefficients of friction and high chemical and heat resistance. However, a sliding member made of PTFE alone is poor in wear resistance and a load carrying capacity, so that the defects of the PTFE are compensated for by adopting the following measures according to the application of use of the sliding member: (a) incorporating into the PTFE a solid lubricant such as graphite, molybdenum disulfide, or the like and/or a reinforcing material such as glass fibers or carbon fibers, and (b) filling the PTFE in the pores of a porous sintered metal layer formed on a steel backing plate and coating the surface of the porous sintered metal layer therewith.
The sliding member having the above-described form (b) is so called a multilayered sliding member, and multilayered sliding members have been proposed in which PTFE or the PTFE containing a filler composed of lead or a lead oxide is filled in the pores of a porous sintered metal layer formed on a steel backing plate and is coated on the surface of the porous sintered metal layer (refer to patent documents 1, 2, and 3).
In addition, a multilayered sliding member has also been proposed in which a melt moldable fluororesin composed of a tetrafluoroethylene-hexafluoropropylene copolymer or a tetrafluoroethylene-perfluoroalkylvinylether copolymer is contained in the PTFE as another filler (refer to Patent documents 4 and 5).